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Agapanthus gall midge is a new species of fly affecting Agapanthus that can cause buds to become deformed and discoloured and fail to flower. It was first noticed in the UK in 2014 but may have been present for several years.
Agapanthus gall midge is a tiny fly that lays eggs on the developing flower buds of Agapanthus. The feeding activities of the larvae inside the buds cause abnormal bud development and infested buds can fail to open.
The species of midge causing this problem is unknown as it is an undescribed species (i.e. new to science). Consequently, very little is known about the biology and lifecycle of this insect. The Plant Health team at RHS Garden Wisley have launched a project to study it, and are asking for help from gardeners who have seen agapanthus gall midge or damaged flowers.
By Post: Please send samples of infested flower heads in sealed bags or containers to: Entomology, RHS Garden Wisley, Woking, Surrey GU23 6QB
By Email: Alternatively, photos including postcode of location of the plant, will help us to map how widespread the midge is in the UK and can be emailed to firstname.lastname@example.org.
If the foliage of Agapanthus appears healthy but the flowers are abnormal in the ways described below, then agapanthus gall midge is most likely the cause:
Currently the RHS does not know which control methods may be effective against agapanthus gall midge. Practical countermeasures and advice on this pest will result from the on-going studies at the RHS.
Gardeners may wish to pick off and destroy galled flower heads as soon as they are seen but there is no evidence yet to show how effective this may be.
The tiny gall midge lays eggs on the plant and the larvae develop inside the individual flower buds or inside the flower head sheath. The larvae can then cause the bud to be deformed and discoloured and often fail to open. The severity of this can range from a couple of buds failing to collapse of the entire flower head.
Infestation can be confirmed by opening the buds or flower heads and looking for the presence of small maggots 1-3mm in length which are a creamy yellow colour. The midge larvae leave the flower head to overwinter and pupate in the soil.
Our research should help us to understand the lifecycle of the midge and determine when the adults are ovipositing (laying eggs).
AgapanthusEucalyptus gall waspFuchsia gall miteHemerocallis gall midge
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